70 NATURAL HISTORY OF KERGUELEN ISLAND. 



oept along the borders of tbe ambulacral grooves, and especially along 

 the anterior one, where they are somewhat larger; beneath they are 

 considerably larger, but not crowded, the largest ones in front, the size 

 decreasing toward the sides, and especially posteriorly. The spines are 

 rather slender, mostly slightly curved, obtuse, and usually flattened at 

 tbe tips ; the larger ones, bordering the ambulacra, are mostly wider, 

 flattened, and canaliculate at the tip ; those within the grooves are very 

 slender, and often capitate; the longer spines of the lower side are 6™"* 

 to 8'"'" in length, and much flatter toward the end. Color of spines, in 

 alcohol, dark greenish brown or olive-green ; test, yellowish brown. The 

 ovaries are composed of raiher large lobules, looking like immature 

 clusters of grapes, and containing large ova. A specimen measures 

 from centre to anterior emargination, 18.5™™ ; toborder of anterior inter- 

 ambulacra, 21™™; to posterior end, 20™™; to lateral border, 18™™ ; to end 

 of antero-lateral ambulacral grooves, 15™™; to end of posterior ones, 

 15™™ ; breadth of antero-lateral grooves, 5 to 5.5™™ ; of posterior ones, 

 4.5™™; depth of each, 5™™; height of test, 21™™; of anal area, 6.5™""; 

 breadth of latter, 4.5™™. 



The specimens regarded as males are also cordate, and decidedly 

 emarginate in front, but the form is more elliptical, owing to the ambi- 

 tus being narrowed opposite and in front of the antero-lateral ambula- 

 cra, so that the width decreases nearly equally from the middle, though 

 somewhat more so posteriorly. The interambulacra are less swollen, 

 and consequently the abactinal area is less sunken. The anterior 

 ambulacral furrow is decidedly sunken, though somewhat less so than 

 in the female; but the four other ambulacra are narrower and very 

 much shallower than in the female, being but little deeper than the 

 anterior odd one, with the sides sloping gradually to the central line, 

 while in the female the sides of the grooves are perpendicular, or even 

 overhanging, with a broadly-rounded bottom. The three genital open- 

 ings are only about half as large as in the female. In the character of 

 the spines, tubercles, peripetalous fasciole, anal area, plastron, actinal 

 area, and lower lip, the two forms agree very closely. 



Kerguelen Island, 7 fathoms; Dr. J. H. Kidder. 



On most of the specimens were several specimens of a small bivalve 

 shell {Lepton parasiticum, Dall) most frequently attached to the under 

 surface, near the mouth. This is evidently a case of " commensualism," 

 for the mollusk is not a genuine parasite but a "messmate" of the echi- 

 uoderm. 



